The present disclosure relates generally to gas turbine engine load bearing cases. More particularly, the present disclosure relates to methods for designing systems for protecting load bearing structural frames from heat exposure.
Turbine Exhaust Cases (TEC) typically comprise structural frames that support the very aft end of a gas turbine engine. In aircraft applications, the TEC can be utilized to mount the engine to the aircraft airframe. In industrial gas turbine applications, the TEC can be utilized to couple the gas turbine engine to an electrical generator. A typical TEC comprises an outer ring that couples to the outer diameter case of the low pressure turbine, an inner ring that surrounds the engine centerline so as to support shafting in the engine, and a plurality of struts connecting the inner and outer rings. As such, the TEC is typically subject to various types of loading, thereby requiring the TEC to be structurally strong and rigid. Due to the placement of the TEC within the hot gas stream exhausted from a combustor of the gas turbine engine, it is typically desirable to shield the TEC structural frame with a fairing that is able to withstand direct impingement of the hot gases for a prolonged period of time. The fairing additionally takes on a ring-strut-ring configuration wherein the struts are hollow to surround the frame struts. Such a fairing is described in U.S. Pat. No. 4,993,918 to Myers et al., which is assigned to United Technologies Corporation. Due to increased engine efficiencies achieved at higher engine operating temperatures, it is desirable to have the TEC capable of withstanding elevated temperatures. It is also, however, desirable to minimize expense of the TEC without sacrificing performance.